Coronary artery disease (atherosclerosis) is a progressive disease in humans wherein one or more coronary arteries gradually become occluded through the buildup of plaque. The coronary arteries of patients having this disease are often treated by balloon angioplasty or the insertion of stents to prop open the partially occluded arteries. Ultimately, these patients are required to undergo coronary artery bypass surgery at great expense and risk. It would be desirable to provide such patients with a treatment that would enhance coronary blood flow so as to preclude the need to undergo bypass surgery or angioplasty.
An even more critical situation arises in humans when a patient suffers a myocardial infarction, wherein one or more coronary arteries or arterioles becomes completely occluded, such as by a clot. There is an immediate need to regain circulation to the portion of the myocardium served by the occluded artery or arteriole. If the lost coronary circulation is restored within hours of the onset of the infarction, much of the damage to the myocardium that is downstream from the occlusion can be prevented. The clot-dissolving drugs, such as tissue plasminogen activator (tPA), streptokinase, and urokinase, have been proven to be useful in this instance. However, as an adjunct to the clot dissolving drugs, it would also be desirable to also obtain collateral circulation to the damaged or occluded myocardium by angiogenesis.
Accordingly, it is an object of the present invention to provide a dose of an angiogenic agent and a mode of its administration to a human heart in need of angiogenesis that provides the human heart with cardiac angiogenesis while minimizing the risk of inducing angiogenesis elsewhere in the body, particularly in an undetected tumor. More particularly, it is a further object of the present invention to provide a therapeutic dose of an angiogenic factor and a mode of its administration to a human patient that provides the desired property of cardiac angiogenesis, such as during the treatment of coronary artery disease and/or post acute myocardial infarction, while minimizing the possibility of an adverse angiogenic effect occurring elsewhere in the body.
Angiogenic agents include the platelet derived growth factors (PDGF), vascular endothelial growth factor-A (VEGF-A), transforming growth factor-β1 (TGF-β1) and the fibroblast growth factors. The fibroblast growth factors (FGF) are a family of at least eighteen structurally related polypeptides (named FGF-1 to FGF-18) that are characterized by a high degree of affinity for proteoglycans, such as heparin. The various FGF molecules range in size from 15-23 kD, and exhibit a broad range of biological activities in normal and malignant conditions including nerve cell adhesion and differentiation [Schubert et al., J. Cell Biol. 104:635-643 (1987)]; wound healing [U.S. Pat. No. 5,439,818 (Fiddes)]; as mitogens toward many mesodermal and ectodermal cell types, as trophic factors, as differentiation inducing or inhibiting factors [Clements, et al., Oncogene 8:1311-1316 (1993)]; and as an angiogenic factor [Harada, J. Clin. Invest., 94:623-630 (1994)]. Thus, the FGF family is a family of pluripotent growth factors that stimulate to varying extents fibroblasts, smooth muscle cells, epithelial cells and neuronal cells.
When any angiogenic agent (or factor) is released by normal tissues, such as in fetal development or wound healing, it is subject to temporal and spatial controls. However, many angiogenic agents are also oncogenes. Thus, in the absence of temporal and spatial controls, they have the potential to stimulate tumor growth by providing angiogenesis. Accordingly, before any angiogenic agent is used as a medicament in human patients, consideration must be given to minimizing its angiogenic effect on undetected tumors. As a result, it is an object of the present invention to provide a dosage of angiogenic agent and a mode of its administration that would provide localized angiogenesis in a targeted organ but which would minimize the risk of enhancing angiogenesis in an undetected tumor elsewhere in the body.
Many of the angiogenic agents (e.g., PDGF, VEGF-A or FGF) have been isolated and administered to various animal models of myocardial ischemia with varying and often times opposite results. According to Battler et al., “the canine model of myocardial ischemia has been criticized because of the abundance of naturally occurring collateral circulation, as opposed to the porcine model, which ‘excels’ in its relative paucity of natural collateral circulation and its resemblance to the human coronary circulation.” Battler et al., “Intracoronary Injection of Basic Fibroblast Growth Factor Enhances Angiogenesis in Infarcted Swine Myocardium,” JACC, 22(7): 2001-6 (December 1993) at page 2002, col. 1. Thus, those of ordinary skill in the art considered the porcine heart to be the model that excelled most in its resemblance to the human heart. Further, Battler points out that “the dosage and mode of administration of bFGF [i.e., bovine FGF-2] may have profound implications for the biologic effect achieved.” Battler, et al., at page 2005, col. 1. Thus, it is a further object of this invention to provide a dosage and a mode of administration of an angiogenic agent that would provide for the safe and efficacious treatment of CAD and/or post MI injury in a human patient. More generally, it is an object of the present invention to provide a pharmaceutical composition and method for administration that would induce angiogenesis in a human heart while minimizing the risk of angiogenesis elsewhere in the body.
The various studies to date on angiogenic agents have administered dosages of the angiogenic agent in the range of 10 μg to 1500 μg. For example, Yanagisawa-Miwa, et al., “Salvage of Infarcted Myocardium by Angiogenesic Action of Basic Fibroblast Growth Factor,” Science, 257:1401-1403 (1992), disclose infusing two 10 μg doses of human recombinant basic FGF (hrFGF-2) in 10 ml of saline over a one minute period into the left circumflex coronary artery (LCX) of dogs after inducing a myocardial infarction by inserting a thrombus into the adjacent left ascending coronary artery (LAD). Yanagisawa-Miwa further discloses that as a result of the intracoronary administration of a total of 20 μg of hrFGF-2 in this canine model, “vessel formation occurred within 1 week after administration of bFGF.” Yanagisawa-Miwa at page 1403. Banai et al., “Angiogenic-Induced Enhancement of Collateral Blood Flow to Ischemic Myocardium by Vascular Endothelial Growth Factor in Dogs,” Circulation, 89(5):2183-2189 (May 1994), discloses successfully inducing coronary angiogenesis (i.e., a 40% increase in collateral blood flow and an 89% increase in the numerical density of intramyocardial distribution vessels) in dogs by administering 45 μg of human recombinant VEGF/day for 5 days/week for 4 weeks to the distal left circumflex artery (LCx) of dogs whose proximal LCx was constricted before the first takeoff branch with an ameroid constrictor and wherein a hydraulic balloon occluder was placed immediately distal to the encircling ameroid. In a similar study, Unger, et al., “Basic fibroblast growth factor enhances myocardial collateral flow in a canine model,” Am. J. Physiol., 266 (Heart Circ. Physiol. 35): H1588-H1595 (1994), disclose enhancing collateral blood flow (i.e., final collateral to normal zone (CZ/NZ) blood flow ratios of 0.49 and 0.35 in the treated and untreated groups, respectively) in dogs by administering a daily bolus of 110 μg of human recombinant basic FGF (the 155 residue form) for 9 days to the distal left circumflex artery (LCx) of dogs whose proximal LCx was constricted before the first takeoff branch with an ameroid constrictor and wherein a hydraulic balloon occluder was placed immediately distal to the encircling ameroid. However, in the above study, Unger was not able to show that his method or dosage induced angiogenesis. Making any assessment based on collateral blood flow more difficult, Unger also discloses that administration of basic FGF causes an acute vasodilatory effect, reducing blood pressure and increasing coronary blood flow. Unger (1994) at page H1590, col. 2 and at page H1592, col. 2.
In an earlier study, Unger, et al., “A model to assess interventions to improve collateral blood flow: continuous administration of agents into the left coronary artery in dogs,” Cardiovascular Res., 27:785-791 (1993), Unger discloses the continuous infusion for four (4) weeks of 30 μg/hr recombinant acidic FGF (i.e., FGF-1) in the presence of 30 IU/hr heparin into the proximal end of the left circumflex artery (LCx) of a dog after constricting the artery for four weeks with an ameroid constrictor, followed by double ligation of the artery and insertion of a catheter for infusing the FGF-1 into the proximal stub of the ligated LCx. Unger (1993) at page 785. Notwithstanding that a total cumulative dose of 10 mg of acidic FGF was infused into the coronary artery of each dog. Unger reported that in this model, “acidic FGF had no demonstratable effect on collateral blood flow . . . ” Unger (1993) at page 785 (Abstract), and at page 790.
Harada, et al., “Basic Fibroblast Growth Factor Improves Myocardial Function in Chronically Ischemic Porcine Hearts,” J. Clin. Invest., 94:623-630 (August 1994), disclose enhancing coronary blood flow and reduction in infarct size in a gradual coronary occlusion model in Yorkshire pigs by extraluminal (periadvential) administration of 8 μg of basic FGF in the form of 4-5 capsules having 1 μg/capsule of basic FGF that are positioned on the proximal left anterior descending artery (LAD) and both proximal and distal to an ameroid constrictor placed on the proximal end of the left circumflex artery (LCx) before the first takeoff branch. Although an express object of Harada's experiment was to “alleviate chronic myocardial ischemia by stimulating angiogenesis” [Harada at page 628], Harada was not able to show angiogenesis. Moreover, Harada concluded that “[I]t is not clear what is the optimal dose of bFGF or the length or route of administration.” Harada at page 629. Separately, Landau et al., “Intrapericardial basic fibroblast growth factor induces myocardial angiogenesis in a rabbit model of chronic ischemia,” Am. Heart Journal, 129:924-931 (1995), discloses that administering 180 ng/day of human recombinant basic FGF (154 residues) into the pericardial space of 2.0-4.3 kg rabbits for 7-28 days, enhances new epicardial small-vessel growth, and that the effect is enhanced by left ventricular hypertrophy. The dosage of basic FGF utilized in Landau, when scaled to the size of a 70 kg man, would correspond to 2.9 μg/day for 7-28 days, or a total dose of basic FGF of 20.3 μg-81.2 μg. Lopez et al., “Angiogenic potential of perivascularly delivered aFGF in a porcine model of chronic myocardial ischemia,” Am. J. Physiol. 274 (Heart Circ. Physiol. 43): H930-H936 (1998), discloses improving myocardial flow and regional and global left ventricular function in Yorkshire pigs by perivascular delivery of 14 μg of a recombinant human aFGF mutein (i.e., Ser-117 aFGF, wherein Ser replaces Cys) that is diffusely distributed in a porous ethylene vinyl acetate (EVA) polymer that is secured with sutures over the proximal left circumflex artery. Lopez reports that the perivascularly delivered aFGF improved blood flow in the compromised region of the heart in animals both “at rest” and “during rapid pacing.” Lopez at page H934, col. 2. However, Lopez was unable to directly attribute the increased blood flow to angiogenesis, citing other possible sources, such as “vasodilation” or “improvements in vascular circulation.”
Finally, U.S. Pat. No. 4,296,100, which issued to Franco on Oct. 20, 1981, discloses a method for treating a myocardial infarction in patients by administering 10 mg to 1 g of 90% pure bovine FGF (pituitary extract) per 100 g of heart tissue as a one-time treatment immediately following infarct. According to Franco, “[a]t least 10 micrograms/100 grams heart is used to achieve the effect desired.” Franco at col. 1, lines 62-64. Franco discloses that the FGF is administered to the heart by a variety of modes, including direct injections into the heart, intravenous injection, subcutaneous injection, intramuscular injection and oral ingestion. Franco at col. 2, lines 63-69. Franco also discloses that his method was able to reduce infarct size (area of scarring or of permanent damage) to one quarter of that in the control. Franco at Table III. According to Franco, the function of the FGF was to “increase blood flow for a sustained period of time after myocardial infarction.” Franco at col. 1, lines 42-43. However, the acute affect of any FGF administration is vasodilation, which inherently increases coronary blood flow. Franco expressly discloses that a histological study “did not show any significant increase in capillary areas in the hearts” as a result of such treatment with 10 μg to 1 g of FGF per 100 g of heart. Franco at col. 4, lines 13-17. Moreover, Franco did not address the issue of whether administering such large doses of FGF would have angiogenic effects in any undiscovered tumors in the body.
Thus, it is an object of the present invention to provide a dosage of an angiogenic agent and a method of administering one or more dosages of the angiogenic agent to a patient in an amount that is effective to induce angiogenesis to an area of the heart in need of angiogenesis. It is a further object of this application to provide a dosage and a method for delivering an angiogenic agent that would provide for a therapeutic effect, including angiogenesis at the target site, while reducing the risk of inducing angiogenesis at an unwanted site elsewhere in the body.
The above-described references and all other references cited herein are expressly incorporated herein in their entirety.